This proposal describes a systems biology approach to biomarker discovery and validation focused on exposure to environmental tobacco smoke (ETS) and its causal link to pancreatic ductal adenocarcinoma (PDAC). Cigarette smoke (CS) is an extremely complex mixture, including numerous tobacco-specific nitrosamines (TSNAs). The present proposal stems from significant advances the investigators have made in the quantification of tobacco-derived compounds and protein biomarkers using stable isotope methodology. CS is the major known environmental risk factor for PDAC, with recent studies implicating both mainstream tobacco smoke and ETS. PDAC is the 4th most common cause of cancer-related mortality in the US and is universally lethal. This research plan is based on four important observations: 1) TSNA metabolism varies greatly among individuals, and higher levels have been associated with lung cancer. 2) TSNAs have also been shown to cause PDAC in laboratory animals. 3) ETS, which contains TSNAs, causes pancreatic inflammation in exposed rats. 4) Pancreatic inflammation and PDAC result in specific changes in proteins secreted by pancreatic cells which we have extensively characterized. Based on these observations, the investigators have developed the following hypotheses: ETS exposes the pancreas to toxic chemicals exemplified by NNK and its metabolite NNAL. Inter-individual differences in metabolism cause serum and tissue levels of these toxic chemicals to vary widely, contributing to differences in PDAC susceptibility. Exposure of the pancreas to these toxic chemicals results in inflammation and secretion of biomarkers that can be quantified and used to asses an individual's risk for PDAC. To test these hypotheses, the following objectives/specific aims will be pursued: 1) To use an in vitro system to characterize and quantify proteomic and metabolomic biomarkers of pancreatic ETS exposure and biological response. 2) To develop panels of biomarkers using stable isotope labeling methodology in order to rigorously assess pancreatic ETS exposure and biological response. 3) To use serum and urine samples from PDAC subjects with quantified levels of ETS exposure and non-exposed controls to refine a biomarker panel of ETS exposure and biological response identified in aim 2. 4) To perform a replication study of the biomarker panel developed in aim 3 to assess the sensitivity and specificity of an individual's risk for PDAC. This proposal will elaborate on the innovative methods developed and significant findings already made by the principal investigator. A unique, interdisciplinary approach has been developed to execute the research described. By achieving these specific aims, this proposal will have a highly significant impact on the field. Furthermore, the investigators' results will shed important light on the etiological role of ETS in PDAC. Biomarkers developed will be used for identifying persons at increased risk for and with early stage PDAC. This translational approach will impact on clinical practice by offering the possibility of surgical resection, which is currently the only realistic option for improving survival from this devastating disease.